Stone in Archaeology Database

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Upper Portland Beds. The Portland Beds can also be found on the Isle of Purbeck where they reach 35 metres in thickness.

Colour ranges from white to buff and blue grey.

There are several main beds which range from a white fine grained limestone (Shrimp Bed) at the top, to hard shelly limestones such as the Blue Bed and Spangle Bed below (Green 1998: 13). The latter is a hard, coarse grained, greyish white stone with numerous blue grey shell fragments (Building Research Establishment n.d.). The Pond Freestone below this, is an oolitic freestone about 1.5m thick, its colour varies but generally it is a fine grained, greyish white stone with faint traces of blue/grey shell. Below this the Under Freestone was the good quality stone sought after by the quarrymen (Stanier 2001: 91).